1. Field of the Invention
The invention relates to a direct-current arc furnace plant comprising a direct-current arc furnace which is disposed on a furnace platform and comprises a furnace vessel surrounded, by a metal shell, at least one electrode connected as a cathode and at least one bottom contact connected as anode and provided with at least one connection fitting, the electrode and the bottom contact being connected via high-current lines to a current supply means disposed alongside the furnace vessel.
In this connection, the invention makes reference to a prior art as revealed, for example, in German Patent 2,558,879.
2. Discussion of Background
In high-power direct-current arc furnaces the high currents flowing in the incoming and outgoing current lines cause deflections of the arc. The arc does not burn vertically. On the contrary, the arc is directed towards the furnace wall and there leads to overheating.
Special guiding of the high-current lines under and at the side of the furnace vessel enables a "centering" of the arc to be achieved. Thus, in U.S. Pat. No. A-4,550,413 and U.S. Pat. No. A-4,557,326 it is proposed to lay these lines in such a way that the magnetic fields produced by the direct current flow act symmetrically on the arc. These measures are, however, expensive and, in addition to the cost, increase the space required for the furnace. Another solution consists in making the electrode, together with the electrode mounting, horizontally movable relative to the furnace vessel, in order thus to compensate for asymmetry in the incoming and outgoing current lines. This measure is also very expensive, because space must accordingly be made in the furnace roof for the path of travel of the electrode.
From German Patent 25 58 879 a direct-current fed arc furnace is known which has a furnace crucible with a nonmagnetic bottom. The bath electrode is disposed asymmetrically in relation to the longitudinal direction of the arc electrode. The high-current lines leading to the bath electrode are disposed in such a manner that at least one conductor is laid under the furnace crucible in a direction such that the current flowing through it flows substantially in the opposite direction to the current in the melt. In order to achieve this current flow, in the known arc furnace the high-current conductors must be disposed high at the top of the crucible, horizontally around the periphery of the furnace crucible. These sections of the high-current conductors thus form a part of the furnace vessel. For operation in the manner customary at present with interchangeable vessels this increases the cost of the vessel. In addition, the protection of these high-current lines on the crucible is expensive.
In another solution, which is the subject of the Applicant's as yet unpublished European Patent Application No. 90116866.6 of Sep. 3, 1990, it is proposed to construct the bottom lining layer of bricks of various conductivities.